Road surfaces (known as pavements) are routinely constructed from asphalt mixture, which is a composite of binder and aggregate. For most pavements, the binder is bitumen, a viscous liquid or a solid consisting essentially of hydrocarbons and their derivatives. However, in recent years synthetic binders have also been used. Synthetic binders, such as Shell's Mexphalte C® possess similar rheological and mechanical properties to the bituminous binders typically used in road applications. The synthetic binders are typically clear, so they are readily pigmented and can be used to obtain coloured asphalt mixture. The synthetic binders can also be used in other applications, such as roofing, waterproofing or sealing applications, e.g. the synthetic binders can be used to seal the gaps between paving stones.
EP 179 510 discloses synthetic binders comprising resin, oil and, optionally, polymer. The resin is a petroleum resin or coumarone-indene resin that contains carboxylic acid, carboxylic acid anhydride or hydroxyl groups. The oil is preferably a mineral lubricating oil extract such as Bright-Stock extract, and the polymer may be a synthetic rubber such as styrene-butadiene-styrene. The use of modified resins containing carboxylic acid, carboxylic anhydride or hydroxyl groups improves the ductility and adhesion properties of the binder compositions.
EP 1 466 878 discloses synthetic binders comprising resin and oil, but not comprising polymer. The resin and oil are renewable raw materials of vegetable origin.
The present inventors have sought to provide an alternative synthetic binder composition. Preferably the binder has improved adhesion properties and preferably the binder uses renewable raw materials.